Apparatus for preparing blood specimens on slides

ABSTRACT

An apparatus for preparing blood specimens on slides having a test surface comprising guide means, a carrier mounted on the guide means for movement back and forth therealong, the carrier providing means for holding the slide to expose its test surface to receive a drop of blood at a predetermined spot thereon. A member extends toward the path of movement of the carrier preferably but not necessarily to engage the test surface of the slide held thereby. Drive means is provided for moving the carrier at a predetermined speed in one direction along the guide means, the carrier being movable in the opposite direction along the guide means to the point at which such a drop of blood on the said predetermined spot just contacts and wets the said member. The member which engages the slide is preferably a resiliently flexible, thin strip-like member which may be resiliently urged against the test surface of the slide to provide, adjacent the test surface and in contact therewith, a portion of the member which is at least slightly curved about an axis extending generally parallel to the test surface and generally perpendicular to the path of movement of the carrier or which is inclined relative to the test surface.

United States Patent Grabhorn I [54] APPARATUS FOR PREPARING BLOODSPECIMENS ON SLIDES [72] Inventor:

Ind.

[73] Assignee: Systematiks, lnc., Indianapolis, Ind.

[22] Filed; Sept. 14, 1970 [21] Appl. No.: 71,728

[52] US. Cl ..l18/l00 [51] Int. Cl ..B05c 11/02 [58] Field ofSearch...118/120, 100, 506; 117/102 R,

117/64 R, 3; 128/2 R, DIG. 5; 23/253 R [56] References Cited UNITEDSTATES PATENTS 3,470,847 10/1969 Chapin et al. ..1 18/100 PrimaryExaminer-M0rris Kaplan Att0rneyI-Iood, Gust, Irish, Lundy & Coffey [5 7ABSTRACT An apparatus for preparing blood specimens onslides Robert H.Grabhorn, Indianapolis,

[151 3,683,850 [4'51 Aug. 15,1972

having a test surface comprising guide means, a carrier mounted on theguide means for movement back and forth therealong, the carrierproviding means for holding the slide to expose its test surface toreceive a drop of blood at a predetermined spot thereon. A memberextends toward the path of movement of the carrier preferably but notnecessarily to engage the test surface of the slide held thereby. Drivemeans is provided for moving the carrier at a predetermined speed in onedirection along the guide means, the carrier being movable in theopposite direction along the guide means to the point at which such adrop of blood on the said predetermined spot just contacts a and wetsthe said member. The member which engages the slide is preferably aresiliently flexible, thin strip-like member which may be resilientlyurged against the test surface of the slide to provide, adjacent thetest surface and in contact therewith, a portion of the member which isat least slightly curved about an axis extending generally parallel tothe test surface and generally perpendicular to the path of movement ofthe carrier or which is inclined relative to the test surface.

24 Claims, 17 Drawing Figures PAIENTED M18 15 1912 SHEET 1 0F 3 INVENTORROBERT H. GRABHORN 2 MI /Y PATENTEDAus 15 I972 3.683., 850

sum 2 or 3 I7FIIIQIIIIIIIIII l I I I /I/ 4 INVENTOR ROBERT H. GRABHORN77Q/MMM/M ATTORNEYS PATENTEDM B 1 I912 3.683; 850

SHEET 3 OF 3 I I I94 INVENTOR. ROBERT H. GRABHORN z/ww/wmgl ATTORNEYSAPPARATUS FOR PREPARING BLOOD SPECIMENS ON SLIDES It is a primary objectof may present invention to provide an apparatus for systematizing thepreparation of blood film specimens on glass slides so that thespecimens can be viewed with a microscope. Specifically, it is an objectof my present invention to provide an apparatus which will take theguesswork out of preparing such specimens on slides by providing meansproportioned and designed correctly and repeatedly to draw a drop ofblood placed on a predetermined spot on the slide into a film which isone cell layer thick.

Such specimens are conventionally and presently prepared on thinrectangular pieces of glass, commonly referred to as slides.conventionally, the technician deposits a drop of blood on one slide andthen manually uses another slide to draw the blood into a thin film and,in some cases improperly to scrape or spread the blood into a thin film.The quality of the film obtained presently depends upon the talent andcapability and care of the technician processing the specimen. It iswell known in the blood testing field that a great many of the slidespecimens made using present techniques are worthless for the testingpurpose intended. This is true because the manual manipulation of thedrop of blood by the second slide often damages blood cells within thedrop and often fails to provide a film which is one cell layer thick.

My apparatus is an important improvement in'that it includes a carriermounted on a guide means for movement back and forth therealong, thecarrier providing means for holding such a slide to expose its testsurface to receive a drop of blood at a predetermined spot thereon. Iprefer to place, on the carrier itself, a spot or dot which will bevisible through the slide so that the technician can place the drop ofblood on the upper surface of the slide, i.e., its test surface, to bein vertical registry with the spot on the carrier. My apparatus includesa member which preferably contacts the test surface of the slide foruniformity purposes. The carrier is preferably manually movable inwardlyto the point at which a drop of blood on the said predetermined spotwill just contact and wet the portion of the applicator member directlyadjacent the test surface. Means are provided for stopping the carrierat this point. At this point, the member contacts and breaks the surfacetension of the drop of blood, and the blood spreads laterally on themember by capillary action. Then, my apparatus includes drive means formoving the carrier at a predetermined constant speed outwardly to movethe drop of blood away from the member. This outward movement, at theproper speed, is effective to draw the drop of blood into a thin filmwhich is of the proper and desired thickness and the cells of which areundamaged by the drawing process.

Utilization of the apparatus defining my present invention, therefore,includes the steps of obtaining and depositing a drop of blood on thetest surface of a slide, moving the slide so that the drop of blood justcontacts and wets the portion of the member held adjacent the testsurface, and thenmoving the slide in the opposite direction at apredetermined speed to draw the drop of blood into a thin film.

It is important to note that my apparatus preferably involves using athin resiliently flexible member held against the test surface on whichthe drop is deposited 4,000 white cells and about 150,000 platelets.Thus,

in such a manner thatthe drop contacts an inclined smooth surface. Thisis in contrast to using the sharp square and flat portion of a slide asthe means for drawing a drop of blood.

I prefer to use an elongated small diameter plastic hose, a length ofwhich has an enlarged cross section, to take the blood specimen.Specifically, in accordance with the disclosures of my copendingapplication Ser. No. 824,977 filed May 15, 1969, now US. Pat. No.3,633,566 and my copending application Ser. No. I65 filed Jan. 2, 1970,now abandoned, I use a small plastic hose or tube, each end of which isconnected to the rear end of a sharpened cannula. One cannula isinserted into a persons vein and the other cannula is sequentiallypenetrated through the closing means or stoppers of tubes which areevacuated. The portion of the hose or tube which has the enlarged crosssection is close to the cannula inserted into the vein so that a drop ofblood of a predetermined size can be obtained simply by squeezing theportion having the enlarged cross section to force a drop out of thecannula and onto a slide. I prefer to use a 21 thin wall cannula topenetrate the vein, and the bore of this cannula will provide a drop ofa desired size when the cannula is first removed from the'vein. i

When the blood droplet is spread into a film, the cells will randomlyspread throughout the film, i.e., some red cells, some white cells andsome platelets will be in any area of the film inspected.- The redcells, white cells and platelets will appear in much the same manner asa group of three differently sized marbles resting on a flat surface toprovide a layer which is one cell thick, but with the cells being ofdifferent size. One cubic millimeter of blood has approximately 4%million red cells,

there are more red cells than anything else appearing in the film drawn.It is important, therefore, in order to study the morphology of thewhite cells and platelets that the film be one cell layer thick.importantly, white cells are studied carefully to classify them as togranulocyte or lymphocyte or variety. Such determinations cannot be madeif the red cells are piled up against the white cells.

Blood film specimens, of course, are investigated under a microscope,and unless the blood is drawn into a film which is one cell thick, it isdifficult to make any sight comparative evaluations at all. Forinstance, if the film is properly one cell layer thick and the cells arenot damaged, a good comparative determination as to the number of whitecells with respect to the number of red cells can be obtained.

Other objects and features of my present invention will become apparentas this description progresses.

To the accomplishment of the above and related objects, my invention maybe embodied in the forms illustrated in the accompanying drawings andthe method described herein, attention being called to the fact,however, that the drawings are illustrative only, and that change may bemade in the specific constructions illustrated and described, or in thespecific steps stated, so long as the scope of the appended claims isnot violated.

In the drawings:

FIG. 1 is a perspective view showing one embodiment of my apparatus;

FIG. la is an exploded perspective view of the internal mechanism of theembodiment of FIG. 1;

FIG. 2 is a transverse sectional view of the embodiment of FIG. 1;

FIG. 3 is a perspective view of a preferred type of applicator memberusable in my apparatus;

FIG. 4 is a longitudinal sectional view of the apparatus of FIG. 1;

FIG. 5 is a fragmentary perspective of a portion of another embodimentof my apparatus, this embodiment including means for mounting a roll oftape and feeding discrete pieces of the tape to be used as test surfacesin lieu of the conventional glass slides;

FIG. 6 is a fragmentary sectional view showing the manner in which aslide is moved in the apparatus of FIG. 1 to draw a film;

FIG. 7 is another fragmentary sectional view similar to FIG. 6 exceptthat it shows the blood droplet contacting the applicator member;

FIG. 8 is another fragmentary sectional view similar to FIG. 6 exceptthat it shows the blood drawn into an exaggerated film;

FIG. 9 is a sectional view of another embodiment of myinvention, thisembodiment including a different drive arrangement than that shown inFIG. 1;

. obtaining the blood droplet;

FIG. 15 is a view of a slide showing diagrammatically the type of filmdrawn by my apparatus; and

FIG. 16 is a view of a slide showing the type of film which is drawn byconventional techniques.

Referring now to the drawings, and particularly to FIGS. 1, la, 2 and 4,it will be seen that my apparatus, indicated generally at 10, includes abase 12 and a housing cover 14 which is attached to the base. The base12 may be provided with rubber-like feet 16 and the housing cover 14 maybe attached to the. base 12 by means such as screws 18 which extendthrough apertures 20 in the base.

My apparatus 10 includes guide means 22 which may be integrally formedwith the base 12 as illustrated in FIG. 2, the guide means includingspaced apart longitudinally extending runners 24, 26 providing,respectively, slideways 28, 30. I provide a carrier 32 mounted on theguide means 22 for longitudinal reciprocable movement back and forththerealong, the carrier 32 providing means for holding a test slide aswill be discussed hereinafter. It will be seen that the carrier slideson the slideways 28, 30.

As best seen in FIGS. 1a and 2, each side of the carrier 32 is providedwith a longitudinally extending slot 34, 36. A pin 38, 40 rigidlyattached to each runner 24, 26 extends into each slot 34, 36 to keep thecarrier 32 on the slideways 28, 30 as the carrier reciprocates.

Each slot 34, 36 is provided with a down-turned portion 42 at its outerend and a down-turned portion 44 at its inner end, the down-turnedportions of slot 34 being seen in FIG. la. These down-turned portions42, 44 provide means for locking the carrier 32 in its inner position orits outer position. Specifically, when the carrier is pushed inwardlyand then raised slightly so that the pins 38, 40 engage the down-tumedportions 42, the carrier is locked in its inner position; and,conversely, when the carrier 32 is pulled outwardly and the pins 38, 40are engaged in the down-turned portions 44, the carrier is locked in itsouter position.

The carrier 32, which is preferably generally horizontally extending,provides upstanding walls 46, 48, 50, 52 bounding a rectangular surface54 having means 56 which may be a spot of paint, tape or the like on itsupper surface. Test slides, one of which is indicated at 58 in FIGS. 1aand 2, are placed on the surface 54 with the sides of the test slideengaging, respectively, the walls 46, 48, 50 and 52. It will beappreciated that the spot 56 will be visible through the clear glassslide 58.

Thus, the spot on the upper, test surface of the slide 58 which is indirect vertical registry with the spot 56 is the aforesaid predeterminedspot on which a drop of blood is deposited in accordance with my presentinvention.

A slider 60 is engaged with the runners 24, 26 to be longitudinallyreciprocable therealong. This slider v60, which is disposed to the rightof the carrier as viewed in FIGS. 1a and 4, acts as a pusher for movingthe carrier 32 outwardly as will be discussed hereinafter. The slider 60may or may not be fastened to the carrier 32. In the illustrativeembodiment, I show a plate 62 mounted on the outer end of the slider 60by means of screws 64, the plate 62 engaging the right-hand end of thecarrier 32. This plate 62. holds down the right-hand end of the carrier32.

In the illustrative embodiment, each runner 22, 24 provides an upright66, 68 between which extends a trunnion 70. A conventional andcommercially available wound strip spring 72 is mounted on the trunnionwith the free end 74 of the spring being connected to the slider 60 bymeans of a screw 76. This type of spring 72 is commonly referred to as aNEGATOR spring.

Referring to FIG. 4, it will be seen that the underneath side of theslider 60 is provided with a cavity 78 in vertical registry with andpenetrated by the shank of the screw 76. A ball bearing 80 is placed inthis cavity to ride on the surface of the base 12, and the shank of thescrew 76 extends into the cavity to engage the ball bearing. Bytightening the screw 76, the ease with which the slider 60 will move onthe runners 24, 26 can be adjusted. Further, in FIG. 1a, I show adashpot 84, the plunger 86 of which is connected to the slider 66 by,for instance, the screw 76. This dashpot 84 works in a conventionalmanner controllably to resist movement of the slider, thereby to controlmovement of the carrier 32 in the direction of the arrow 90. The mannerin which a dashpot provides this function will be understood by thosefamiliar with mechanisms.

In FIGS. la and 4, I show an arrow 88 representing the movement of thecarrier 32 inwardly and an arrow 90 representing movement of the carrieroutwardly.

The spring 72 is a drive means for moving the carrier 32 at apredetermined speed in one direction as indicated by the arrow 90 alongthe guide means 22. The carrier 32 is movable in the opposite directionas indicated by the arrow 88 along the guide means 22 to the point atwhich a drop of blood placed on the aforesaid predetermined spot of thetest surface of the slide 58, i.e., in vertical registry with the spot56, contacts and wets an applicator member which will be discussed indetail hereinafter.

A finger engageable push member 92 is provided for manually pushing thecarrier 32 inwardly to the point at which the drop of blood contacts theapplicator member. Stop means are provided for defining this point. Forinstance, the engagement of the pins 38, 40 in the left-hand ends of theslots 34, 36 may serve as a stop means for the carrier 32 when it movesin the direction of the arrow 88. It will be appreciated that any suchstop means may be used.

Referring now to FIGS. 1, 6, 7 and 8, it will be seen that I haveillustrated an applicator member 100 including an applicator portion 102and a gripping portion 104. The gripping portion 104 is provided withside notches 106, 108 and the applicator portion 102 terminates, at itsdistal end, with a transversely extending straight edge 110. As bestseen in FIGS. 1 and 2, the housing 14 is provided with an opening 112 atits upper, left-hand end as viewed in FIG. 1, this opening 112terminating with-a slot 114 into which the applicator member 100 isinserted. The slot 114 provides laterally extending notches 116, 118which coopera tively engage, respectively, the notches 106, 108 securelyto hold the applicator member 100 in position relative to the carrier32. It will be appreciated that this means of holding the applicatormember securely relative to the carrier 32 is illustrative and that anynumber of such means may be used to accomplish the same purpose.

The applicator portion 102 is preferably a thin resiliently flexiblestrip-like plastic member. The applicator member 100 is-preferably heldrelative to the carrier 32 in such amanner that the applicator portion102 will be resiliently urged against the test surface of the slide 58as best seen in FIGS. 6, 7 and 8. Referring to FIGS. 6, 7 and 8 it willbe seen that the applicator portion 102 is held in such a manner that itis curved to provide, adjacent the test surface and in contacttherewith, a portion 122 curving about an axis which is above thesurface 58 and extending perpendicular to the guide means 22, i.e., thepath of movement of the carrier 32. This portion 122 provides an outerperipheral surface which is contacted by the blood drop B. Specifically,as shown in FIG. 6, the blood drop B is placed at the aforesaidpredetermined spot on the test surface. of the slide 58. Then thecarrier 32 is moved in the direction of the arrow 88. The previouslydiscussed stop means stops the carrier 32 at the point at which the dropB just contacts and wets the outer peripherally curved surface of theportion 122 adjacent the test surface of the slide 58. As soon as thedrop B contacts the portion 122, the blood spreads laterally against theportion 122 by capillary action because the surface tension of the dropis broken by the applicator member. Then, the carrier 32 is moved in thedirection of the arrow 90 at a predetermined preferably constant minedspot on which it was initially placed. The movement of the slide in thedirection of the arrow causes the blood in the drop B to be drawn into afilm.

If the carrier 32 is moved too fast in the direction of the arrow 90,the film will be broken. If the carrier 32 is moved too slow in thedirection of the arrow 90, the blood will be drawn into a film which istoo thick. Experimentally I have determined that a carrier speed ofapproximately 1 inch per second is satisfactory. It will be appreciated,however, that this speed will depend upon the particular configurationof the applicator member, etc.

Referring now to FIGS. 3 and 11, it will be seen that I have shown anapplicator member having two applicator portions 132, 134 extending awayfrom a central portion 136. Each portion 132, 134 s provided withnotches 138 which perform the same function as the notches 106, 108discussed in conjunction with the applicator member 100. Each applicatorportion 132, 234 is bent or formed as indicated at 140 a short distancefrom its distal edge 142. When the applicator member 130 is snapped intothe slot .114, the distal edge 142 of its applicator portion 132 or 134will engage and extend transversely across the test surface of the slide58 as shown in FIG. 11. There will be a portion 144 extending betweenthis distal edge 1.42 and the bend line 140, this portion 144 providinga downwardly facing inclined surface extending toward the test surfaceof the slide 58 and in the direction of the arrow 90, i.e., thedirection'in which the slide 58 is pushed inwardly. The slide 58 isstopped by the aforesaid stop means at the point at which the blood dropB contacts and wets this inclined surface as illustrated in FIG. 11.Then, the slide is moved in the direction of the arrow 88 to move thedrop B away from the applicator portion 132, 134. I prefer to constructthe applicator member so that the portion 144 (FIG. 11) is inclined atan angle of approximately 25 relative to the test surface of the slide58. It will be appreciated that this angle of inclination also dependson several factors including the size and shape of the applicator'memberand that the angle of inclination may be from approximately 25 toapproximately 45 relative to the test surface of the slide 58.

Referring now to FIGS. 12 and 13, it will be seen that there isillustrated an applicator portion 144' directly adjacent the testsurface of the slide 58. The applicator member providing this portion144' has its distal edge 142' cut or otherwise formed as indicated at toprovide spaced apart contact points 152, 154 which engage the lateraledges of the test surface of the slide and a straight edge 151 extendingtransversely across and above the test surface, the contact points 152,154 being effective to hold the straight edge 151 at the desired heightabove and in parallelism with the test surface. This straight edge 151may only be held, for instance, 0.00l inch above the test surface.

It is not absolutely vital that the applicator member itself touch thetest surface of the slide. It is only necessary that the applicatormember have a portion which is close enough to the test surface of theslide to be contacted and wetted by the blood drop placed upon the testsurface I have found that it is more convenient to engage the free endof the cantilevered applicator member with the test surface of the slidein such a manner that the blood drop will engage an inclined surface ora curved surface of the applicator member in the same manner each time afilm is made. It will be appreciated that the drop B (FIG. 11) willengage more area of the downwardly facing inclined surface of theportion 144 than it would if the portion 144 were extendingperpendicularly to the test surface of the slide 58.

Referring now to FIG. 5, it will be seen that l have constructed theslider indicated at 60' in such a manner that it provides means 160, 162for mounting a roll of tape 164 for movement with the carrier indicatedat 32. This system of FIG. is adapted to feed discrete pieces of thetape 164 to the carrier 32 so that these discrete pieces of tape canserve as test slides. Specifically, tape is fed under a knife-edgebracket 166 as in dicated by the arrow 168 to cover the upwardly facingsurface of the carrier 32 on which the spot 56 is marked. The blood isthen dropped onto the spot of the tape which is in directe registry withthe spot 56 so that the smear or film can be made on the surface of thetape. The means for supporting the roll of tape includes a pair ofsupport arms 160 extending rearwardly and upwardly from the slider 60'and a trunnion 162 extending between the support arms 160. The onlysignificant difference between the structure of FIG. 5 and the structureof FIGS. la, 2 and 4 is that the roll of tape is added so that discretepieces of the tape can be used as test surfaces.

Referring now to FIGS. 9 and 10, it will be seen that I have shownanother embodiment of my apparatus, indicated generally by the referencenumeral 10', this embodiment being similar to the embodiment of FIGS.

1a, 2 and 4, except that a different drive means 180 is utilized todrive the carrier 32 in the direction of the arrow 90. Like referencenumerals in FIGS. 9 and 10 represent like parts in FIGS. 1, la, 2 and 4.

The drive means 180 is a commercially available spring-type drive motorhaving an output gear 182 which I use to drive a rack 184 whichreciprocates with the carrier 32. Thus, my apparatus of FIGS. 9 and 10basically includes a spring motor 180 and transmission means (outputgear 182 and rack 184) drivingly connecting the spring motor to thecarrier 32. The spring motor of the drive means 180 is mounted above thepath of the rack 184 on standoffs 186, 188 to hold its output gear 182in mesh with the rack 184. While the drive means 180 is commerciallyavailable and need not be discussed in detail herein, it does include astrip spring 190 which is also of the type usually referred to as aNEGATOR spring and portions of which are wrapped about a trunnion 192and another axis concentric with the output gear 182. The drive means180 includes a fly wheel and clutch arrangement (the housing for whichis indicated at 194) which controls the output speed of the gear 182.The gear 182 is drivingly connected to the fly wheel and clutcharrangement by conventional gearing, the housing for which is in dicatedat 196. Energy is stored in the spring 190 when the carrier 32 ismanually pushed in the direction of the arrow 88 to the point at whichthe drop of blood contacts the applicator member. Then, promptly, theperson making the specimen removes his hand to permit the drive means toreturn the carrier 32 in the direction of the arrow 90.

I have found that I am able to obtain the proper rate of movement of thecarrier using the spring-type motor discussed generally in FIGS. 9 and10.

In the structure of FIGS. 9 and 10, the rack 184 is rigidly fastened toa slider 185 which corresponds to the slider 60 discussed previously.Further, in FIGS. 9 and 10, I show spring-loaded detent means 198arranged to hold the carrier 32 in its illustrated position in FIG. 9 tokeep the pin 38 in the down-turned portion 42 of the slot 34 to hold thecarrier in its inner position. Referring now to FIG. 14, it will be seenthat l have illustrated a cannula 200, cannula gripper 202 and a hose204, a portion 206 of which is enlarged as illustrated. In accordancewith the disclosures of my aforementioned patent applications, thecannula 200 is inserted into a persons vein so that the blood flowsthrough the cannula and the hose 204. Generally, a number of bloodspecimens are deposited into test tubes from the hose 204. When thecannula 200 is removed from the vein, a blood drop of a preferred sizecan be accurately positioned on the test surface of a slide in registrywith the' spot 56 on the carrier simply by placing the sharpened end ofthe cannula at that spot on the slide and then gently applying pressureto the enlarged portion 206. The pressure applied to the enlargedportion 206 will cause a drop of blood to leave the end of the cannula200. The size of the drop of blood will depend on the bore size of thecannula 200. I prefer to use a No. 21 thin wall cannula 200, and thebore size of this particular cannula will provide a blood drop of thepreferred size.

Referring now to FIGS. 15 and 16, a comparison of the type of film madeby my apparatus with the type of film made by conventional processes canbe had. FIG. 15 is an illustration of a film made by my apparatus. Theportion of the indicated at 210 is a longitudinally short film which is,for-instance, five cells thick. Then the film gets thinner as indicatedby the area 212 which may be, for instance two cells thick. The balanceof the test area indicated at 214 is a film which is one cell thick asdesired. It will be appreciated that more than half of the test surfaceincludes a film which is one cell thick. In FIG. 16, the film on thearea indicated at 216 will be quite thick. The film on the areaindicated at 218 will be progressively thinner but it will be severalcells thick. Finally, the film on the area indicated at 220 willgenerally be one cell thick if the conventional process is handledproperly. The length and width of the one cell thick film provided by myapparatus 10, 10' is considerably greater than the length and width ofthe film area indicated at 220 in FIG. 16.

From the above description, it will be appreciated that I have providedan apparatus for using the apparatus which greatly systematizes themaking of blood film specimens on slides, i.e., the making of what isknown in the medical profession as peripheral smear specimens. When myapparatus 10 is used, the angle ofinclination of the applicator memberrelative to the test surface of the slide is always the same, the speedby which the blood drop is drawn into a film is always the same, theamount and size of the blood drop is always the same, the pressure withwhich the applicator member is held against the test surface is alwaysthe same, the age of the blood drop deposited on the test surface whenthe smear is made is always the same, and the location of the blood dropon the slide and the length of the smear is always the same. Withrespect to the age of the blood when the smear is made, I contemplatethat the blood drop will be deposited onto the test surface of the slidejust as soon as the cannula 200 is withdrawn from the vein. As soon asthe blood drop is placed on the slide, the technician merely has to pushinwardly on the carrier 32 until it stops moving, this whole processtaking place in a matter of a very few seconds.

What is claimed is:

1. An apparatus for preparing blood specimens on slides having a testsurface comprising guide means, a carrier mounted on said guide meansfor movement back and forth therealong, said carrier providing means forholding such a slide to expose its test surface to receive a drop ofblood at a predetermined spot thereon, means for defining said spot, amember extending toward the path of movement of said carrier and thetest surface of the slide held thereby, means for holding said memberrelative to said guide means, and drive means for moving said carrier ata predetermined speed in one direction along said guide means, said carrier being movable in theopposite direction along said guide means tothe point at which a drop of blood on said predetermined spot of such aslide contacts said member to effect a capillary spread of said bloodand whereby, upon return movement of the carrier in said one direction,a blood smear is obtained.

2. The apparatus of claim 1 in which said member is resiliently flexibleand in which said holding means is positioned relative to said carrierso that said member is resiliently urged against the test surface of theslide to provide, adjacent the test surface and in contact therewith, aportion of said member curving about an axis to provide an outerperipheral surface to be contacted by such a drop of blood.

3. The apparatus of claim 2 including means for stopping movement ofsaid carrier in said opposite direction at said point, said stoppingmeans being positioned so that, when said carrier is at said point, sucha drop of blood on said spot will contact and wet said portion of saidmember.

4. The apparatus of claim 3 in which said axis of curvature extendsgenerally parallel to the test surface and generally perpendicular tothe path of movement of said carrier, said member being cantileveredfrom said holding means so that said curved portion is its free endportion.

5. The apparatus of claim 1 in which the portion of said member adjacentand against the test surface is formed to extend toward the test surfaceand in said opposite direction, and including means for stoppingmovement of said carrier in said opposite direction at said point, saidstopping means being positioned so that, when said carrier is at saidpoint, such a drop of blood on said spot will contact and wet bycapillary action said formed portion.

6. The apparatus of claim 5 in which said member is cantilevered fromsaid holding means so that said formed portion is its free end portion.

7,. The apparatus of claim 6 in which said member is a thin, strip-likemember, said formed portion being curved about an axis extendinggenerally parallel to the test surface and generally perpendicular tothe path of movement of said carrier.

8. The apparatus of claim 7 in which said member is resilientlyflexible,said holding means being positioned relative to said carrier so thatsaid member is resiliently urged against the test surface of the slide.

'9. The apparatus of claim 1 in which said drive means includes a springfor moving said carrier in said one direction away from said point.

10. The apparatus of claim 9 including means for controllably resistingmovement of said carrier by said spring, thereby to determine the speedof movement in said one direction away from said point.

11. The apparatus of claim 1 including means for mounting a roll of tapeand feeding discrete pieces of said tape to said carrier, said discretepieces serving'as the slides.

12. The apparatus of claim 11 in which said mounting means is connectedto said-carrier for movement therewith.

13. The apparatus of claim 1 in which the portion of said memberadjacent the test surface is formed to provide an inclined surfaceextending the test surface and in said opposite direction and includingmeans for stopping movement of said carrier in said opposite directionat said point, said stopping means being positioned so that, when saidcarrier is at said point, such a drop of blood on said spot will contactand wet said inclined surface.

14. The apparatus of claim 13 in which-said member provides spaced apartcontact points which engage the test surface and a straight edge portionextending trans versely across and above the test surface, said contactpoints being effective to hold said straight edge portion at the desiredheight above and in parallelism with the test surface.

15. The apparatus of claim 14 in which there are two of said contactpoints engaging, respectively, opposite side edges of the test surfaceand in which said straight edge portion extends between said contactpoints.

16. The apparatus of claim 13 in which said portion of said member isinclined at an angle of approximately 25 relative to the test surface.

17. The apparatus of claim 13 in which said portion is inclined at anangle of from approximately 25 to approximately 45.

18. The apparatus of claim 1 in which said drive means includes a springmotor, and transmission means drivingly connecting said spring motor tosaid carrier.

19. The apparatus of claim 18 in which said transmission means includesa rack connected to said carrier and extending in the direction of saidguide means and gear means drivingly connecting said rack to said springmotor. 7

20. The apparatus of claim 19 including braking means drivinglyconnected to said transmission means and arranged to control the speedat which said rack is driven.

21. The apparatus of claim 20 in which energy is stored in said springmotor by manually moving said carrier in said opposite direction to saidpoint.

1] l2 22. The apparatus of claim 21 including means for means forstopping movement of said carrier in said opstopping movement of saidcarrier in said opposite it di ti at s id point, said stopping meansqlrection at said'poinfi'said PPR E me an$ being p being positioned sothat, when said carrier is at said tioned so that, when said carrier isat said point, such a point, such a drop of blood on Said Spot willContact drop of blood on sald spot will contact said member.

and wet said inclined surface.

24. The apparatus of claim 23 wherein the means defining said spot isvisible through said slide.

23. The apparatus of claim 21 in which the portion of said memberadjacent the test surface is formed to provide an inclined surfaceextending toward the test surface and in said opposite direction, andincluding -3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3 683 8 50 Dated August 15 1972 lnventofls) Robert H.Grabhorn It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 1 after the title, "may" should be my Column 6, line 20,"s" should be is line 23, "132 ,234" should be 132 ,134

Column 8, line 14 should be the beginning of a new paragraph; line 39,after "the" and before "indicated" insert film Column 10, line 26 (Claim13, line 3) after "extending" and before "the", insert toward Signed andsealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

1. An apparatus for preparing blood specimens on slides having a testsurface comprising guide means, a carrier mounted on said guide meansfor movement back and forth therealong, said carrier providing means forholding such a slide to expose its test surface to receive a drop ofblood at a predetermined spot thereon, means for defining said spot, amember extending toward the path of movement of said carrier and thetest surface of the slide held thereby, means for holding said memberrelative to said guide means, and drive means for moving said carrier ata predetermined speed in one direction along said guide means, saidcarrier being movable in the opposite direction along said guide meansto the point at which a drop of blood on said predetermined spot of sucha slide contacts said member to effect a capillary spread of said bloodand whereby, upon return movement of the carrier in said one direction,a blood smear is obtained.
 2. The apparatus of claim 1 in which saidmember is resiliently flexible and in which said holding means ispositioned relative to said carrier so that said member is resilientlyurged against the test surface of the slide to provide, adjacent thetest surface and in contact therewith, a portion of said member curvingabout an axis to provide an outer peripheral surface to be contacted bysuch a drop of blood.
 3. The apparatus of claim 2 including means forstopping movement of said carrier in said opposite direction at saidpoint, said stopping means being positioned so that, when said carrieris at said point, such a drop of blood on said spot will contact and wetsaid portion of said member.
 4. The apparatus of claim 3 in which saidaxis of curvature extends generally parallel to the test surface andgenerally perpendicular to the path of movement of said carrier, saidmember being cantilevered from said holding means so that said curvedportion is its free end portion.
 5. The apparatus of claim 1 in whichthe portion of said member adjacent and against the test surface isformed to extend toward the test surface and in said opposite direction,and including means for stopping movement of said carrier in saidopposite direction at said point, said stopping means being positionedso that, when said carrier is at said point, such a droP of blood onsaid spot will contact and wet by capillary action said formed portion.6. The apparatus of claim 5 in which said member is cantilevered fromsaid holding means so that said formed portion is its free end portion.7. The apparatus of claim 6 in which said member is a thin, strip-likemember, said formed portion being curved about an axis extendinggenerally parallel to the test surface and generally perpendicular tothe path of movement of said carrier.
 8. The apparatus of claim 7 inwhich said member is resiliently flexible, said holding means beingpositioned relative to said carrier so that said member is resilientlyurged against the test surface of the slide.
 9. The apparatus of claim 1in which said drive means includes a spring for moving said carrier insaid one direction away from said point.
 10. The apparatus of claim 9including means for controllably resisting movement of said carrier bysaid spring, thereby to determine the speed of movement in said onedirection away from said point.
 11. The apparatus of claim 1 includingmeans for mounting a roll of tape and feeding discrete pieces of saidtape to said carrier, said discrete pieces serving as the slides. 12.The apparatus of claim 11 in which said mounting means is connected tosaid carrier for movement therewith.
 13. The apparatus of claim 1 inwhich the portion of said member adjacent the test surface is formed toprovide an inclined surface extending the test surface and in saidopposite direction, and including means for stopping movement of saidcarrier in said opposite direction at said point, said stopping meansbeing positioned so that, when said carrier is at said point, such adrop of blood on said spot will contact and wet said inclined surface.14. The apparatus of claim 13 in which said member provides spaced apartcontact points which engage the test surface and a straight edge portionextending transversely across and above the test surface, said contactpoints being effective to hold said straight edge portion at the desiredheight above and in parallelism with the test surface.
 15. The apparatusof claim 14 in which there are two of said contact points engaging,respectively, opposite side edges of the test surface and in which saidstraight edge portion extends between said contact points.
 16. Theapparatus of claim 13 in which said portion of said member is inclinedat an angle of approximately 25* relative to the test surface.
 17. Theapparatus of claim 13 in which said portion is inclined at an angle offrom approximately 25* to approximately 45*.
 18. The apparatus of claim1 in which said drive means includes a spring motor, and transmissionmeans drivingly connecting said spring motor to said carrier.
 19. Theapparatus of claim 18 in which said transmission means includes a rackconnected to said carrier and extending in the direction of said guidemeans and gear means drivingly connecting said rack to said springmotor.
 20. The apparatus of claim 19 including braking means drivinglyconnected to said transmission means and arranged to control the speedat which said rack is driven.
 21. The apparatus of claim 20 in whichenergy is stored in said spring motor by manually moving said carrier insaid opposite direction to said point.
 22. The apparatus of claim 21including means for stopping movement of said carrier in said oppositedirection at said point, said stopping means being positioned so that,when said carrier is at said point, such a drop of blood on said spotwill contact said member.
 23. The apparatus of claim 21 in which theportion of said member adjacent the test surface is formed to provide aninclined surface extending toward the test surface and in said oppositedirection, and including means for stopping movement of said carrier insaid opposite direction at said point, said stopping means beingpositioned so that, when said carrier is at said point, such a drop ofblood on saId spot will contact and wet said inclined surface.
 24. Theapparatus of claim 23 wherein the means defining said spot is visiblethrough said slide.